1. Field of the Invention
The present invention relates to a liquid crystal operation device and an image processing system using the same for wide use in industrial products capable of image processing and diagram processing and products for factory automation.
2. Description of the Related Art
Introduction of computer technologies in recent years brought about remarkable developments in image processing technologies in the fields of medical equipment, remote sensing, robotic vision, and the like. Today, digital image processing technologies are rapidly improved in combination with the advanced LSI technologies for wide use in consumer products including audiovisual appliances and office automation equipment.
The digital image processing technologies realize the following through operations using pixels (addition, subtraction, etc.), data conversion, histogram preparation, marginal distribution preparation, logic operation (contraction, expansion, outline extraction, etc.), and labeling.
(1) Visualization of X-ray images, temperature distribution images, etc.,
(2) Clarification of images by noise removal and brightness compensation,
(3) Extraction and measurement of features of images, and
(4) Image recognition and image understanding.
FIG. 10 illustrates general image processing steps for image recognition. An image data (analog signal) obtained by a TV camera 81 is converted into a digital signal by an A-D converter 82, and the digital signal is stored in an image memory 83. Based on the stored signal, an external operation device 84 performs image processing and image measurement, thereby performing image recognition. The image data processed in such a system has the following features.
(1) Two-dimensional,
(2) Large in amount; for example, approximately 256KB to IMB per a plane, and
(3) Gradation (number of bits) per an image is diversified.
In order to perform high speed digital processing of an image data having such features, the data stored in the image memory 83 should be processed at a high speed. For improving the processing speed in the image memory 83, various systems including the following representative ones have been proposed.
(1) Complete parallel processing system. Basic operation modules each corresponding to a pixel holding a two-dimensional image data are two-dimensionally provided, and the modules are simultaneously operated in parallel. In this system, real-time image processing is realized.
(2) Local parallel processing system. Access to data and operation are performed in parallel in a local area having 3.times.3 to 15.times.15 pixels. Such local processing is sequentially performed for all the pixels.
(3) Pipeline processing system. Image data are sequentially sent to processing modules connected to one another as a pipe line, and the processing results are sequentially obtained after a certain delay time.
However, none of these systems have sufficient processing capability at present. These systems have inconveniences such that it takes a long time to process a huge amount of image data and also to transfer data between an external memory device and a main memory device (image memory). The complete parallel processing system has other inconveniences because of an enlarged circuit scale and a higher manufacturing cost thereof.
Under the circumstances, an image processing system which processes a huge amount of image data at a high speed and simultaneously recognizes the image has been demanded.
To answer this demand, application of a liquid crystal device to image processing has been proposed (The Transactions of the Institute of Electronics, Information and Communication Engineers of Japan, C-II, Vol.-J73-C-II, No. 11, pp. 703 to 712, 1990).
FIG. 11 illustrates an image operation system 90 which is proposed in the above-mentioned literature. The image operation system 90 includes a light source 97 emitting red, blue and green light beams. The light beams are transmitted sequentially through a color polarizing plate 91, a liquid crystal display device (referred to as the LCD device, hereinafter) 92, a color polarizing plate 93, an LCD device 94, and a color polarizing plate 95. The LCD devices 92 and 94 are, for example, of an active matrix type and perform black and white display. The light outgoing from the color polarizing plate 95 indicates the operation result. The color polarizing plates 91, 93 and 95 linearly polarize a light beam having a specified wavelength, but transmits a light beam having any other wavelength without such polarization.
FIGS. 12a through 12c illustrate a performance of the image operation system 90. In these figures, the hatched areas are rotation regions which transmit light while rotating the light, and blank areas are transmission regions which transmit light without rotation. FIG. 12a concerns an image operation system 90a for obtaining an AND (G1.multidot.G2) of images G1 and G2 displayed in the LCD devices 92 and 94. In this operation, the color polarizing plates 91, 93 and 95 linearly polarize all the light beams having a wavelength of .lambda..sub.1 in an identical direction. In this construction, light beams which are linearly polarized by the color polarizing plate 91 are rotated at a specified angle by a rotation region of the LCD device 92 but are transmitted as linearly polarized light beams through a transmission region of the LCD device 92. The light beams transmitted through the transmission region are transmitted through the color polarizing plate 93 as they are, and then are rotated by a rotation region of the LCD device 94 but are transmitted through a transmission region of the LCD device 94 as they are. The light beams rotated by the LCD device 94 are shielded by the color polarizing plate 95, but the light beams transmitted through the LCD device 94 without rotation are transmitted through the color polarizing plate 95. The light beams rotated by the LCD device 92 are shielded by the color polarizing plate 93. As a result, a semicircular image is displayed as an AND operation result on a display plane 96.
FIG. 12b concerns an image operation system 90b for obtaining an OR (G1+G2) of the images G1 and G2. Light beams having wavelengths of .lambda..sub.2 and .lambda..sub.3 are used. The color polarizing plate 91 linearly polarizes light beams having a wavelength of .lambda..sub.2. The color polarizing plate 93 linearly polarizes light beams having wavelengths of .lambda..sub.2 and .lambda..sub.3. The color polarizing plate 95 linearly polarizes light beams having a wavelength of .lambda..sub.3. In this construction, light beams having a wavelength of .lambda..sub.2 are linearly polarized by the color polarizing plate 91, but light beams having a wavelength of .lambda..sub.3 are transmitted through the color polarizing plate 91 without such polarization. Among the light beams linearly polarized by the color polarizing plate 91, only the light beams transmitted through the circular transmission region of the LCD device 92 are transmitted through the color polarizing plate 93 based on the above-mentioned principle. Then, the light beams are transmitted through the transmission region of the LCD device 94 without rotation but are rotated by the rotation region of the LCD device 94. However, since all the light beams having a wavelength of .lambda..sub.2 are transmitted through the color polarizing plate 95, a circular image is obtained on the display plane 96.
The light beams having a wavelength of .lambda..sub.3 are linearly polarized by the color polarizing plate 93 for the first time. Among the light beams linearly polarized by the color polarizing plate 93, only the light beams transmitted through the rectangular transmission region of the LCD device 94 are transmitted through the color polarizing plate 95, whereby a rectangular image is obtained on the display plane 96. As a result, an image made of the circular image G1 and the rectangular image G2 is obtained as the OR operation result on the display plane 96.
FIG. 12c concerns an image operation system 90c for obtaining an inverted image of an EXCLUSIVE-OR (G1 EXOR G2) of the images G1 and G2. A monochromatic light having a wavelength of .lambda..sub.4 is used. The color polarizing plates 91 and 95 linearly polarize light beams having a wavelength of .lambda..sub.4. The color polarizing plate 93, which transmits such light beams without polarization, may be eliminated or formed of a transparent glass. In this construction, light beams having a wavelength of .lambda..sub.4 are linearly polarized by the color polarizing plate 91. The light beams are transmitted through the transmission region of the LCD device 92 without rotation but are rotated at a specified angle by the rotation region of the LCD device 92. Among the light beams rotated by the LCD device 92, the light beams transmitted through the rotation region of the LCD device 94 are further rotated, thereby becoming parallel to the polarizing direction of the color polarizing plate 95. The light beams rotated either by the LCD device 92 or 94 are shielded by the color polarizing plate 95. The light beams transmitted through the transmission region of the LCD device 92 and then the transmission region of the LCD device 94 reach the display plane 96. As a result, an inverted image of the XOR of the images G1 and G2 is obtained as the operation result on the display plane 96.
In the above-mentioned system 90, fundamentally two LCD devices are used for an optical operation. Such a construction requires precise positional alignment of these LCD devices, which is troublesome. Moreover, formation of an image in each LCD device requires data transfer from an image generator. The data transfer takes a long time, which prolongs the processing.
In sequential image processing operations performed by the conventional system 90, light from an object as a reference is received by an imaging device such as a CCD and is converted to an electric signal. Then, such electric signals are sequentially sent to the LCD device 94, and the processed image is displayed therein. An image for operation is displayed on the LCD device 92 by another electric signal, and then a desired light is transmitted through the system for operation. In this case also, photoelectric conversion is necessary in an optical path of either one of the two LCD devices 92 and 94. Therefore, parallel processing cannot be stably performed, which spoils the efficiency of optical processing.
In the system using an LSI as is shown in FIG. 10, complete parallel processing is most desirable, but enlarges the circuit scale. Further, the chip area is enlarged, and the manufacturing cost is significantly high.